Wireless networks are becoming increasingly common. Many wireless networks, such as IEEE 802.11 wireless local area networks (WLANs), employ contention-based media access techniques to provide transmitting devices with access to a wireless communications medium (e.g., a channel). For instance, IEEE 802.11 WLANs employ carrier sense multiple access (CSMA) techniques.
CSMA techniques involve a transmitting device verifying the absence of other traffic before sending a transmission on a shared communications medium. This verifying involves the transmitting device “listening” for any network traffic. Once the transmission is sent, the transmitting device will typically await an acknowledgment of successful receipt (an “ACK”) by the intended receiving device.
However, IEEE 802.11 standards do not provide for receiving devices to send negative acknowledgements (NACKs) in response to corrupted transmissions that were sent using CSMA techniques. Instead, if the transmitting device does not receive an ACK within a predetermined time, it may pursue sending a retransmission after a waiting period (a “back-off” interval). Although proprietary NACKs exist, they do not provide assistance in overcoming particular forms of interference.
Contention-based techniques work well when packet errors are primarily due to collisions between transmissions from network stations. However, these techniques are not as effective in dealing with co-channel interference, such as bursty out-of-band emissions, platform noise, and/or hidden node collisions.